U.S. patent number 4,233,650 [Application Number 05/947,093] was granted by the patent office on 1980-11-11 for brightness control for fiber optical lamps.
This patent grant is currently assigned to Ernst Leitz Wetzlar GmbH. Invention is credited to Horst Frimmel, Willi Hagner.
United States Patent |
4,233,650 |
Hagner , et al. |
November 11, 1980 |
Brightness control for fiber optical lamps
Abstract
Disclosed is a brightness control device for use with fiber
optical lamps, comprising a diaphragm which is arranged
unilaterally in the light beam between the lamp light source and
the light entrance area of the fiber optical conductor. The
diaphragm comprises a variable size diaphragm which is designed
such that the cross-section of the light entrance area of the fiber
optical conductor is asymmetrically and unilaterally reduced in
order to maintain a constant lamp color temperature and emission
characteristic.
Inventors: |
Hagner; Willi (Solms,
DE), Frimmel; Horst (Hermannstein, DE) |
Assignee: |
Ernst Leitz Wetzlar GmbH
(DE)
|
Family
ID: |
6021022 |
Appl.
No.: |
05/947,093 |
Filed: |
September 29, 1978 |
Foreign Application Priority Data
Current U.S.
Class: |
362/552; 362/283;
362/322 |
Current CPC
Class: |
G02B
5/005 (20130101); G03B 9/06 (20130101) |
Current International
Class: |
G03B
9/02 (20060101); G02B 5/00 (20060101); G03B
9/06 (20060101); F21V 007/04 (); G02B 009/00 ();
F21V 017/02 () |
Field of
Search: |
;362/17,18,32,35,282,283,322,323 ;350/96.18,96.19,206,207,208 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Walsh; Donald P.
Attorney, Agent or Firm: Schwartz, Jeffery, Schwabb, Mack,
Blumenthal & Koch
Claims
What is claimed is:
1. A brightness control device for use with fiber optical lamps
which include an optical fiber bundle having a light entrance area
and a light source which directs a light beam towards said light
entrance area, comprising a diaphragm arranged unilaterally in the
light beam between said light source and said light entrance area,
said diaphragm having a variable size and a shape such that the
cross-section of the light entrance area of said fiber bundle is
asymmetrically and unilaterally reduced.
2. The brightness control device of claim 1, wherein said diaphragm
comprises a circular sector of variable arc length having its apex
located on the optical axis of said light beam.
3. The brightness control device of claim 2, wherein said diaphragm
comprises a plurality of circular, rotatingly engaged diaphragm
rings, each of which has a circular sector-shaped portion which
projects into the free area enclosed by said ring with the apex of
said sector located approximately on the optical axis of said light
beam, said sectors being superposable with respect to one
another.
4. The brightness control device of claim 3, wherein said diaphragm
rings are rotatingly engaged by means of a pin and slot arrangement
mounted on the circumference of said rings such that rotation of a
first of said diaphragm rings engages and then rotates the
remainder of said rings in consecutive fashion.
5. The brightness control device of claim 4, wherein the pins of
said pin and slot arrangement comprise short tongues formed by
bending the material punched out from the slots at the base
thereof.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a brightness control device for
use in lamps of the type in which light is emitted by means of a
fiber optical conductor, i.e., the so-called fiber optical
lamps.
It is known in the art that the brightness of the light emitted by
fiber optical lamps may be controlled by inserting a variable
resistance or a regulating transformer into the circuit of the
lamp, or by utilizing phase-shifting controls for this purpose.
With each of these arrangements, the operating voltage of the lamp
and thus the color temperature of the light emitted is altered,
although the emission characteristics of the fiber optical
conductor or conductors, respectively, are preserved, i.e., the
angle of radiation and the magnitude of the illuminated area are
maintained constant.
It is also known to effect the regulation of brightness by means of
a built-in iris diaphragm. With this arrangement, the color
temperature of the lamp remains constant, but the angle of
radiation of the optical fiber conductor is changed.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a
brightness control device for fiber optical lamps which in the
course of its operation avoids the aforementioned disadvantages of
the prior art.
It is a specific object of the present invention to provide a
brightness control device for fiber optical lamps which effects a
reduction in brightness without altering the color temperature of
the lamp and the emission characteristics of the fiber optical
conductor.
In accordance with the present invention, these and other objects
are attained through the provision of a brightness control device
which comprises a variable size diaphragm arranged unilaterally in
the light beam between the lamp light source and the light entrance
area of the fiber optical conductor, the shape of the diaphragm
being such that the cross-section of the optical fiber bundle is
reduced asymmetrically and from one side only. The present
invention thus provides a brightness control device wherein the
color temperature and the emission characteristics of the lamp are
maintained constant by obviating the necessity for interference
with the power supply of the lamp, and by asymmetrically and
unilaterally reducing the light flux impinging on the entrance area
of the optical conductor. While the instant brightness control
device asymmetrically reduces the angle of light received on the
entrance area of the optical conductor, due to the multiple
reflection of the light beams within the optical fiber bundle, the
emission characteristics of the optical fiber conductor remain
unaffected.
In the preferred embodiment of the instant invention, the diaphragm
is designed in the shape of a sector of a circle, the apex of the
circular sector being located approximately on the optical axis of
the path of the illuminating beam.
In a particularly preferred embodiment of the present invention,
the diaphragm preferably comprises a plurality of circular,
rotatingly engaged, diaphragm rings, each of the rings having a
circular sector-shaped portion which extends from the ring into the
free area enclosed thereby, with the apex of each circular sector
being located approximately on the optical axis of the illuminating
beam, the several circular sectors being congruent with respect to
one another. With this construction, the rings may be rotatingly
displaced in relation to each other from a position in which all of
the circular sectors are superposed to form a single packet of a
relatively small area, to a position in which they are located more
or less adjacently to each other, thus covering a correspondingly
larger area.
In order to achieve this rotational displacement of each sector in
a simple manner, in a further embodiment of the instant invention,
the foremost ring is equipped with a handle whereby the ring may be
rotated manually, and the remaining rings are connected to the
foremost ring via a pin-and-slot arrangement, in which driving
tongues engage elongated slots in the rings whereby the sectors are
displaced in a fan-like manner, rotation of the foremost ring
serving to engage and then rotate the remaining rings in
consecutive fashion. The driving tongues may comprise pins, or
alternatively may be formed by bending the material punched from
each slot at the base thereof.
Other objects, features, and advantages of the instant invention
will become apparent to the skilled artisan upon examination of the
following detailed description of the instant invention, taken in
conjunction with the figures of drawing, wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a vertical sectional view of a fiber optical lamp
utilizing the brightness control device of the present invention in
a first embodiment;
FIG. 2 is a frontal sectional view along line II--II of FIG. 1;
FIG. 3 illustrates an alternative embodiment of a fiber optical
lamp employing the brightness control device of the present
invention; and,
FIG. 4 is a perspective view of the brightness control device
according to the instant invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, FIG. 1 illustrates a conventional fiber
optical lamp having a housing 1 and containing therein a lamp 2,
the beam of which is conducted in part directly and in part by
reflection from concave mirror 3, to a first lens 4. A second lens
5 reproduces the light source at the entrance area 6a of a fiber
optical conductor 6, which conducts the light over a suitable
distance and emits the light through opening 6b.
In the fiber optical conductor, the individual fibers are arranged
so that each fiber is contacted with light having an angle of
incidence of .alpha..sub.o -.alpha..sub.x. To attain light
attenuation, therefore, the beam of light must be dimmed uniformly,
percentage-wise, over the entire range of the angle of incidence.
Statistical distribution of the individual fibers in the fiber
optical conductor is not necessary. The direction of incidence of
the beam is also immaterial, because of the multitude of total
reflections in the individual fibers.
In the embodiment of the drawings, a variable arc-length, sectorial
diaphragm is arranged between the lenses 4 and 5, comprising the
three diaphragm rings 7, 8, 9. As seen in FIGS. 2 and 4, each
diaphragm ring is formed with a sector 7a, 8a, 9a, respectively,
which extends into the free area bounded thereby. The diaphragm
rings 7, 8, and 9 are superposed upon each other and may be rotated
in relation to each other in an infinitely variable manner between
two terminal positions. In one of the terminal positions, the
sectors 7a, 8a, 9a are superposed upon each other so that only the
cross-sectional area of one sector acts effectively as the
diaphragm in the path of the beam. In the other terminal position
the sectors are located adjacent to each other and overlap only
slightly. This position is illustrated in FIGS. 2 and 4 wherein it
may be seen that one half of the path of the light beam is
blocked.
While the brightness control device of the instant invention has
been described with reference to a three ring diaphragm, each ring
having its own sector, it is contemplated by the instant invention
that any number of such rings having circular sector portions of
any suitable arc length, such as would be obvious to those skilled
in the art, may be employed without departing from the spirit
thereof.
Upon rotation of the rings of the diaphragm relatively to each
other, the sectors are displaced in a jalousy-like fashion, wherein
the leading ring engages the ring following it in rotation. This
mode of displacement is obtained by means of a pin and slot
arrangement on the rings, as can be best seen in FIG. 4.
FIG. 4 shows the rings of the diaphragm in the same terminal
position as shown in FIG. 2. The leading ring 7 is equipped with a
pin 7b. The ring 8, next in line, is provided with an elongated
slot 8b, which is engaged by the pin 7b of the preceding ring 7.
The ring 8 in addition is equipped with a tongue 8c, bent out from
the elongated slot 8b, which engages in turn the elongated slot 9b
of the next succeeding ring. The ring 9 is mounted in a stationary
manner.
A handle 10 is mounted on the leading ring 7 in order to manually
rotate this ring. When the diaphragm ring 7 is rotated manually by
the handle in the direction of the arrow A in FIG. 4, the pin 7b
thereof slides initially into the elongated slot 8b of the
succeeding ring 8, whereby the sectors 7a and 8a become
increasingly superposed upon each other. When the pin 7b engages
the end of the elongated slot 8b, the ring 8 is also entrained,
until all three sectors 7a, 8a, and 9a are superposed upon one
another. The pin 8c and the elongated slot 9b serve to limit the
degree of rotation. When the ring 7 of the diaphragm is rotated in
the opposite direction, the sectors 7a, 8a, 9a are pulled
apart.
In the closed position of the diaphragm, the sectors 7a, 8a, and 9a
are superposed upon each other, forming thereby a relatively small
area, the magnitude of which is a function of the number of the
diaphragm disks and the size of the sectors in the path of the
light beam. In order to eliminate even this slight loss of light
attendant to the presence of the diaphragm in the light path, which
is hardly noticeable in actual practice, the complete diaphragm may
be constructed so that it may be swung out of the path of the light
beam in a lateral direction.
FIG. 3 illustrates another typical embodiment of a fiber optical
lamp, utilizing the brightness control device of the present
invention. In this embodiment, an eliptical reflector lamp 11 is
used as the source of light. The sectorial diaphragm is located
between the lamp and the light entrance area of the fiber optical
conductor, and functions identically as has been described in
detail above.
While the invention has now been described in terms of certain
preferred embodiments, and exemplified with respect thereto, the
skilled artisan will readily appreciate that various modifications,
changes, omissions and substitutions may be made without departing
from the spirit thereof. It is intended, therefore, that the
present invention be limited solely by the scope of the following
claims.
* * * * *